MOMBASA: Somali militants killed two people in Kenya's northeastern Mandera county on Monday when they sprayed their bus with bullets, Kenyan police and a spokesman for the al Shabaab rebel group said.

The attack comes about a year after al Shabaab gunmen stormed a bus, carrying mostly teachers, from Mandera to the capital Nairobi, and executed 28 non-Muslim passengers.

That episode shocked Kenya and led to a shake-up of security ministers.

Since the 2014 attack, buses carrying passengers from Mandera have been given police escorts, but Kenya Police spokesman Charles Owino said that that had not happened in this case because the bus had bypassed a police roadblock.

Owino said that in addition to the two deaths, four people were wounded.

Sheikh Abdiasis Abu Musab, al Shabaab's military spokesman, said the group was responsible. "We were behind the bus attack," he told Reuters in a statement. "Some of the Christian enemies died and others were injured."

Al Shabaab has said it will continue its attacks on Kenya until Nairobi withdraws troops from an African Union force fighting the militants in Somalia. It has also said northeastern Kenya should be part of Somalia.

Kenya's northeastern border with Somalia is widely considered a security weak spot, given the challenge of policing such a long frontier, poor coordination between security services, and a culture of corruption that allows anyone prepared to pay a bribe to pass unchallenged.